Check if a string is substring of another | C # program to check if a string is substring of other . ; Returns true if s1 is substring of s2 ; A loop to slide pat [ ] one by one ; For current index i , check for pattern match ; Driver code
using System ; class GFG { static int isSubstring ( string s1 , string s2 ) { int M = s1 . Length ; int N = s2 . Length ; for ( int i = 0 ; i <= N - M ; i ++ ) { int j ; for ( j = 0 ; j < M ; j ++ ) if ( s2 [ i + j ] != s1 [ j ] ) break ; if ( j == M ) return i ; } return - 1 ; } public static void Main ( ) { string s1 = " for " ; string s2 = " geeksforgeeks " ; int res = isSubstring ( s1 , s2 ) ; if ( res == - 1 ) Console . Write ( " Not ▁ present " ) ; else Console . Write ( " Present ▁ at ▁ index ▁ " + res ) ; } }